Web tensioner for high speed printer

ABSTRACT

A high speed printer for use with data processing equipment wherein the printing is produced by feeding a paper web past a ribbon and rotating type roll, and striking the web against the type roll and ribbon with a plurality of hammers to produce the printed line. The web is fed in a path past the type roll by a tractor feed arrangement disposed after the type roll, and tensioning means is provided before the type roll to maintain tension in the web being drawn past the print station. A second tensioning means in the form of a pair of tensioning rolls is provided along the paper path after the tractor arrangement to produce an opposite or counter driving force to that force produced by the type roll action on the web during printing.

United States Patent Familant [4 1 Dec. 26, 1972 [54] WEB TENSIONER FORHIGH SPEED 3,161,277 10/1964 Smithbauer .197/l33 R PRINTER FOREIGNPATENTS OR APPLICATIONS [72] Inventor: Stanley G. Familant, Framingham,

Mass 576,895 6/1959 Canada ..226/177 1,022,370 3/1966 Great Britain....;..197/l33 [73] Assignee: Honeywell Inc., Minneapolis, Minn.

Primary Examiner-Robert E. Pulfrey [22] @1970 AssistantExaminer-Clifford D. Crowder [21] Appl. No.: 52,224 Attorney-Fred Jacoband Leo Stanger 52 us. 01 ..197/133 P, 101/93 0, 101/228, [.57] ABSTRACT226/195 A high speed printer for use with data processing [51] Int. Cl...B41j 15/16 equipment wherein the printing is produced by feed- [58]Field of Search ..197/ 133, 49; 226/177, 195; ing a paper web past aribbon and rotating type roll, 101/228, 93 C and striking the webagainst the type roll and ribbon with a plurality of hammers to producethe printed [56] References Cited lineQThe web is fed in a path past thetype roll by a tractor feed arrangement disposed after the type roll,UNITED STATES PATENTS and tensioning means is provided before the typeroll 3,568,812 3/1911 Eitel ..197/133 R tensim in-the web being draw Pthe 3,396,890 8/1968 Fulton ..226/177 Ptint Station- A ten-51mins meansthe 3,416,051 12 1968 Pinto et al ..101 228 ux Of a P i of tensioningr0118 is Provided along the P p 3,401,397 9/1968 Blakistone et al...226/195 X path after the tractor arrangement to produce an op-3,259,288 7/1966 Wassermann ..197/133 R UX posite or counter drivingforce to that force produced 3,550,745 12/1970 Bisone et a1. ..197/133 Rby the type roll action on the web during printing. 3,421,612 1/1969Pitt ..197/133R 3,440,955 4/1969 Howard et al ..197/ 133 R X 14 C15, 6Drawing Figures PATENTED DEC 2 8 I972 SHEET 1 OF 3 L1 Fi.1 Q3

INVENTOR Stanley 6. Fami/anf Attorney PATENTED DEC 2 6 I972 SHEET 3 BF 3OON mt Ow Om 03 mm OS 09 Om mn OK. 00 Om 0% 0w 282m "55 .m mo

3% 3% 3? 3? 3% 0mm .llillll HEB 2% 53 95226 5243283 359 Attorney WEBTENSIONER FOR HIGH SPEED PRINTER A BACKGROUND OF THE INVENTION paper webis fed past a rotating type roll having a plurality of characters on itsperiphery, the print-out taking place by means of selected hammersforcing the paper against a ribbon and the type roll when the desiredcharacter is in registry with the hammer. While this type of printingdevice has' become popular for high speed printers, a problem inherentinthis arrangement is that of verticalmisregistration of the paper withthe print roll causing a staggered line of print to occur. Whileacertain amount of misregistrationcan be tolerated as a trade-off for theincreased speed available from this type of printer, it has long beendesirable to provide a drum type printer wherein this problem ofmisregistration is minimized to produce a line of print wherein anyvertical misalignment of one character relative to the others is notdiscernable to the most critical eye.

It is therefore an object of the present invention to provide a highspeed drum type printer which has the characteristic of improved linequality.

A further object of the invention is to provide a drum type printerwhich produces a line of print having improved vertical registration ofthe characters.

Another object of the invention is to provide a drum type printerwherein a force is provided opposite the force produced by the type rollmotion on the paper to insure vertical print registration between thepaper web and the print roll.

SUMMARY OF THE INVENTION The above objects, and other objects which willbecome apparent as the description proceeds, are achieved by providing adocument printer of the type described having a mechanism for advancinga web along a path into printing alignment with the printing mechanism,and wherein the advancing mechanism includes means disposed along theweb path after the printing mechanism for driving the web along thepath, and roller means disposed along the web path for applying acontrolled tensile force to a web portion between the printing mechanismand the roller means. In a more detailed aspect, the roller meansincludes a pair of rolls, one drivingly engaged with a web portion andthe other idlingly engaged with the opposite side of the web andapplying a pre-set normal force to the drive roll to produce thecontrolled tensile force in the web.

BRIEF DESCRIPTION OF THE DRAWINGS The various advantages and features ofthe invention will be more readily apparent from the followingdescription, taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a schematic elevational view showing a drum type printerhaving the present invention employed therein;

FIG. 2 is a schematicview showinga portion of the structure of FIG. Ilaid out in a straight line configuration for clarity, and showing ingreater detail elements of FIG. 1;

FIG. 3 is a top plan view taken along the lines III-III of FIG. 1, andshowing details of the structure employed in that portion of theschematic view taken on an enlarged scale for clarity;

FIG. 4 is an elevational view of the structure of FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,and in particular to FIG. 1, there is 'shown'a high speed drum typeprinter 10 having a compartment 12 in which the forms to be printed, orother paper supply, are stored to be fed into the printer mechanism. Thepath of the paper web P is indicated by the arrows, as passing from thecompartment 12 through the various portions of the printer 10 whichportions'have been shown schematically in FIG. 1. As will be observed byfollowing the path of the paper web P, a tractor assembly 13, which maybe of any type well-known in the art for causing movement of the paperweb, is engaged with the web and effective to move the paper asindicated upwardly from the compartment 12. As the paper web P is movedfrom the compartment 12, it passes through a lower guide means 14 andinto a lower tension means which is provided in the form of an S bararrangement. The lower tension means comprises a pair of plates .15 and15', each having a radial-surface, one opposite the other, over whichthe web I passes, and av movable stationary bar 16 which is disposed inclose proximity to the plates 15 and 15' causing the paper to assume acircuitous path around the bar 16.

The bar 16 is adjustable in the horizontal direction (by means notshown) to produce more, or less, tension in the portion of the web Pbetween the tractor 13 and the bar 16 to maintain the web substantiallyflat as it passes through the print mechanism. While the specific S barconfiguration shown has been advantageously employed as means forproviding tension in the web portion above-mentioned, it will be evidentto those familar with the art that other tensioning means could beprovided at this point in the web path to produce a drag force in thatportion of the unprinted paper web P.

Referring still to FIG. 1, and following the path of web from the S bar16, it will be noted that the paper web P passes through a printmechanism having a type roll 17, over the tractor l3, and into the .mainpaper guide mechanism 18. Adjacent the exit portion of the paper guidemechanism 18 there is provided an upper tensioning device 119 whichserves to control the tension in the portion of the paper web after thetype roll 17 in a manner which will be described hereinafter. From theupper tensioning device 19, the paper web passes over an exit guide 20and thence to a stacking prises a drive roll 22 and an-idler roll 23which are positioned on opposite sides of the web path, the drive rollbeing rotated by a suitable drive motor (not shown) in a direction tourge the paper web P along the prescribed path, while the idler roll isadjustably mounted so as to produce a normal force against the driveroll 22 with the paper web P therebetween. it will furtherbe notedthatthe type roll 17 is rotated in a direction such that the roll surfaceadjacent the. web is moving counter to the direction of web travel. Asis typical in print arrangement of this type, a movable'rib bon '24 isprovided adjacent the path of the web P, and a plurality of printhammers 25 located on the opposite side of the web, the print hammersbeing selectively actuatedas the desired character comes into registrytherewith to'produce a line of print. While the type roll 17 may be ofany configuration well-known in the art, the present inventionhas' beenused to great advantage with a type roll wherein the characters areoffset in groups as used with the time shared hammer drive arrangementshown and described in US. Pat. No. 3,461,796 to Belson et al., andassigned to the assignee of the present invention. With the use of theoffset characters on the type roll, as described in the aforementionedreference, the problem of vertical print line registration in high speeddrum printers becomes more critical, and the solution to this problemwhich is disclosed in the present invention may be best appreciated.

The tractor or form driving device 13 is shown in FIG. 2 to be one ofthe type having studs which are engaged in perforations at the peripheryof the web to drive the web P along the prescribed path. As such tractorarrangements are well-known in the art, and are advantageously used in awide varietyof computerprinter applications, further details of thedevice 13 are considered to be unnecessary for the purpose of thepresent description.

. Referring now to FIGS. 3, 4, and S, the reader will be more adequatelyapprised of the mode of operation of the web 'tensioning device 19 whichis shown in greater mechanical detail than hereinbefore in these views.As will be observed, a pair of plates 41 and 42 are provided to supportthe tensioning device 19 and the paper guide mechanism 18 as referred toabove. In the embodiment shown, the drive roll 22 is divided into aplurality of segments 22a, 22b, etc., while the idler roll 23 may beformed of a plurality of like rolls 23a, 23b, etc., each being of acorresponding width to, and in registration with the segments 22a, 22b,etc. It will further be noted that the guide mechanism 18 is comprisedof a plurality of wire elements 43 which serve to form the lower portionof the guide mechanism 18 while a plurality of bent arcuate wire members44 serve to form the upper portion of the guide mechanism 18. It shouldtherefore be evident that the segmentation of the rolls 22 and 23 isdesigned such that the guide elements 43 are allowed to project betweenthe rolls. The guide mechanism 18 is thereby effective to direct the webP into the rolls 22, 23 after it enters the gap between the upperportion 44 and the lower portion 43 of the guide mechanism. Further, byproviding the arcuate portion 44, a paper web end which is thrust by thetractor 13 into the gap between .the guides 44 and 43 is guideddownwardly by the portion 44 and into the rolls 22 and 23 duringstart-up of the printer.

Referring to FIG. 5, the idler roll 23 is shown as fixedly mounted to ashaft 30 rotatably mounted in the plates 41 and 42. An arm 31 is affixedat one end to the shaft 30 and has the opposite end attached to a spring32 connected to the plate 41. A disk 33 provided with a cam surface atits periphery is mounted on a shaft 34 and is rotated by means of acrank 35 connected thereto. it will be observed that the cam surface ofthe disk 33 is in contact with 'the arm 31 which is biased toward thedisk by the spring 32(Movetnent of the crank 35 such that the arm '31 isrotated counter clockwise is thereby effective to cause the roll 23 toapply anincreased pressure on the drive roll 22. Thus, there is provideda micrometer-like adjustment for producing the desired pressure betweenthe rolls 22 and 23,'which importance will become evident as thedescription proceeds.

It should here be mentioned, that the outer surface of the roll 22should be of material which exhibits a relatively high coefficient offriction to produce the required driving force on the web, and thusimpart the desired tension into the web. Advantageously, a Hycar rubbermaterial was used in the embodiment described, however, any material ofthis type having a coefficient of friction in the range of from 0.3 to0.5 could likewise be employed. With regard to the surfaces of the idlerrolls 23, it has been found that the coefficient of friction should besubstantially less on this. surface due to the requirement that a smallamount of slippage takes place when the paper web P is not being movedby the tractor 13. Thus, the idler rolls 23 depicted herein areconstructed of a nylon or other plastic material with a relatively lowcoefficient friction, in the order of from 0.5 to 0.1 to allow someslippage to take place. It will also be evident that the surface of theidler roll 23 should be of a relatively smooth material such thatmarking or erasure of the printed form will not take place due to theroll being in contact with the printed surface of the web P (the highcoefficient. drive roll 22 being in contact with the unprinted side ofthe web).

In operation of the printer it) with a computer or other input device,the web P is stepped through the print mechanism as each successive lineof print becomes available for print-out. While the complex electronicsand logic involved in such a system have not been herein described, itis considered to be within the capabilities of one skilled in the art toprovide a system of this type. However, it should here be brought outwith regard to this specific disclosure that the type roll rotation,ribbon movement, tractor operation, and drive roll rotation areconnected into such system. In

the present system, when a new line of print is called for, the tractoris energized to step the paper to a next line position, the drive rollbeing continuously operated during this time period. When the tractor isstopped, the drive roll continues to rotate applying a tensile force tothe web P. The force created by the roll is sufficient to overcome theforce created by the 'type roll, hammer contact with the paper web, andmaintain the web in vertical print line registration. It is apparent atthis point that continued rotation of the drive roll and idler rollcombination, if effective to feed the web, would possibly tear the-webfrom the tractor, or cause localized damage to the web at the point ofcontact. However, with the combination of surface friction coefficients(as herein described) on rolls 22 and 23, slippage takes place and onlythe desired tensile force results. In the present system, the drive rollis rotated with the initiation of each print instruction and continuesfor four seconds after the print instruction is completed. In off-linemode of printing, or should print instructions occur at less than 4second intervals, the drive roll operates continuously.

In operation therefore, it has been seen that the paper web P is movedin increments through the print mechanism by the tractor 13 and fedbetween the rolls 22 and 23. As the paper is fed, the printing of a lineoccurs through the actuating of the print hammers 25 to engage the weband force the web against the type roll 17, and thus produce the line ofprint. The time that the print hammers remain engaged with the type rollis generally referred to as the contact time. During this time period,the type roll will pull the slack out of the paper web P and evenslightly distort the feed holes of the web which is driven by thetractor arrangement 13. it will be evident therefore, that the problemof misregistration lies in the fact that the print drum 17 will rotateand carry the web P out of registration during the time that the printhammers 25 are in contact with the web P, ribbon 24, and type roll 17combination. The form or web B will attempt to recover its originalposition because of the elastic nature of the paper. Ideally, the formor web P should spring back to its original position after each printingoperation, however, this is not the case in prior art devices. It shouldhere be noted that the worse possible case of niisregistration generallyoccurs when printing groups of the same characters that follow oneanother around the periphery of the type roll 17. This is no doubt dueto the fact that the time is insufficient in this mode of operation forthe elasticity to recover the paper to its original position.

Referring still to FIGS. 1 and 2, it will be seen that by employing thecontinuously rotating drive roll 22 in combination with the idler roll23, a device is provided which is effective to produce a force in theweb P which is of sufficient magnitude to ofi-set that force produced bythe type roll 17 on the web P, and relative motion between the roll 17and the web does not occur. Thus, the principle or theory of operationof the tensioning device 19 in the printing system is that the rolls 22and 23 produce an opposite driving or counter force in the web to thatproduced by the type roll 17 to prevent web movement. The ability of therolls 22 and 23 to produce the reactive force is dependent substantiallyon the coefficient of friction between the drive rolls 22 and the paper,and the normal force produced between the idler roll 23 and the driveroll. The rolls 22 and 23 in combination, therefore provide a dynamicweb tension device which is constantly attempting to recover the paperweb P or form that is continuously being 6 [j urged out of registrationby the type roll 17 and hammers 25. As a result of using the tensioningdevice 19 in the present invention, in combination with the S bar 16which serves to react the force of the tensioning device 19, it ispossible to getthe proper forms tensionfor both the printing and feedingoperation, with little compromise to either mode of operation. I

Referring to the curves shown in FIG. 6, the reader will betterappreciate the effect of the tensioning device 19 in'overcoming theproblem of misregistration in a printer device of the type described.The data plotted was collected by operating a Model 1 12 Printermanufactured by the Honeywell Corporation having the present inventionembodied therein. The printer was operated at 275 lines per minute usinga single part pound form as the print web. As will be noted, with boththe worse case lines as shown by the upper plot and the standard-lines,an idler normal force in the area of to 200 grams is effective toproduce a vertical line misr'egistration of less than '4 mils, which isa marked improvement over prior art devices and acceptable for mostcomputer print-out purposes.

What is claimed is:

l. A document printer havinga mechanism for ad vancing a web along apath into printing alignment with a printing mechanism having a typeroll disposed for rotation adjacent said web for contacting said webduring the printing operation, said advancing means having incombination, means disposed along said path after the said printingmechanism for driving said web along said path, and rotatable rollermeans contacting said web along said path after said driving means forapplying a continuing dynamic tensile force during rotation thereof to aweb portion extending between said printer mechanism and said rollermeans and in a direction opposite to the direction. of the forceproduced on said web by the rotation of said type roll,

said roller means being effective to move said web at the point ofroller means contact an increment of length sufficient to compensate forstretching of said web portion and thereby maintain a tensile force ofsubstantially constant value on said web during the printing operation.

2. The printer as set forth in claim 1 wherein said roller meanscomprises a drive roll with a surface having a high coefficient offriction contacting said web, and

means for rotating said roll in a direction to produce said force onsaid web to drive said web away from said printing mechanism.

3. The printer as set forth in claim 2 wherein said roller means furthercomprises an idler roll with a surface having a coefficient of frictionsubstantially less than that of said drive roll surface, said idler rollbeing positioned to apply a normal force to said drive roll with saidweb disposed therebetween.

4. The printer as set forth in claim 3 which further includes means foradjustably increasing or decreasing the magnitude of normal forceapplied to said drive roll by said idler roll.

5. The printer as set forth in claim 4 wherein said drive roll surfaceis a rubber composition and said force applied to said drive roll bysaid idler roll is greater than 100 grams.

6. The printer as set forth in claim 2 wherein said printing mechanismcomprises a plurality of printhammers disposed adjacent said type rolland movable to a position to force said web into driving relation withsaid type roll during rotation thereof.

7. The printer as set forth in claim 6 wherein said web is provided withperforations at an edge, andsaid driving means is provided with aplurality of studs engageable with said perforations to so drive saidweb along said path. i I

8. A printer as set-forth in claim-1 which further includes othertensioning means disposed along said path before said printing mechanismfor applying a static drag force to said web in the opposite directionto said a tensile force.

9. in a document printer wherein a feed mechanism is disposed after saidprinting mechanism for driving a paper web through said printingmechanism and wherein said printing mechanism comprises a ribbon androtatable print roll disposed adjacent one side of theweb and aplurality of movable hammers disposed on the opposite side of said webfor striking said web and forcing it into contact with said ribbon andprint roll combination to produce a line of print, the imsile force.

to produce a tensile force insaidweb opposite to a tensile forceproduced in said web by contact of said rotating print roll and ribboncombination with said web when struck by one of said-hammers.

1 1. The structure of claim 10 wherein said tensioning means furthercomprises an idler roll with a surface having a coefficient of frictionsubstantially less than that of said drive roll surface, said idler rollbeing positioned to'apply a force to said-drive roll with said webdisposed therebetween. -j

12. The structure of claim 11 which further includes means foradjustably increasing or decreasing the magnitude of force applied tosaid drive roll by said idler roll.

13. A printer-as set forth in claim 9 which further includes othert'ensioning means disposedialong said path before said printing meansforapplying a static drag force to said web in the opposite direction tosaid ten- 14. The method of feeding a paper web through a printer of thetype wherein a ribbon and rotating type roll are disposed adjacent oneside of the web and a plurality of movable hammers are disposed adjacentthe opposite side of the web to strike the web and force it into theribbon and rotating type roli to form a line of print on the web, whichincludes the steps of advancing the web in increments past the typeroll, printing upon web 0 site the f rce roduced on said web bcontact oald type roll an ribbon combination wleh said web to maintain lineregistration of the web with said print roll during printing of anentire line.

1. A document printer having a mechanism for advancing a web along apath into printing alignment with a printing mechanism having a typeroll disposed for rotation adjacent said web for contacting said webduring the printing operation, said advancing means having incombination, means disposed along said path after the said printingmechanism for driving said web along said path, and rotatable rollermeans coNtacting said web along said path after said driving means forapplying a continuing dynamic tensile force during rotation thereof to aweb portion extending between said printer mechanism and said rollermeans and in a direction opposite to the direction of the force producedon said web by the rotation of said type roll, said roller means beingeffective to move said web at the point of roller means contact anincrement of length sufficient to compensate for stretching of said webportion and thereby maintain a tensile force of substantially constantvalue on said web during the printing operation.
 2. The printer as setforth in claim 1 wherein said roller means comprises a drive roll with asurface having a high coefficient of friction contacting said web, andmeans for rotating said roll in a direction to produce said force onsaid web to drive said web away from said printing mechanism.
 3. Theprinter as set forth in claim 2 wherein said roller means furthercomprises an idler roll with a surface having a coefficient of frictionsubstantially less than that of said drive roll surface, said idler rollbeing positioned to apply a normal force to said drive roll with saidweb disposed therebetween.
 4. The printer as set forth in claim 3 whichfurther includes means for adjustably increasing or decreasing themagnitude of normal force applied to said drive roll by said idler roll.5. The printer as set forth in claim 4 wherein said drive roll surfaceis a rubber composition and said force applied to said drive roll bysaid idler roll is greater than 100 grams.
 6. The printer as set forthin claim 2 wherein said printing mechanism comprises a plurality ofprint hammers disposed adjacent said type roll and movable to a positionto force said web into driving relation with said type roll duringrotation thereof.
 7. The printer as set forth in claim 6 wherein saidweb is provided with perforations at an edge, and said driving means isprovided with a plurality of studs engageable with said perforations toso drive said web along said path.
 8. A printer as set forth in claim 1which further includes other tensioning means disposed along said pathbefore said printing mechanism for applying a static drag force to saidweb in the opposite direction to said tensile force.
 9. In a documentprinter wherein a feed mechanism is disposed after said printingmechanism for driving a paper web through said printing mechanism andwherein said printing mechanism comprises a ribbon and rotatable printroll disposed adjacent one side of the web and a plurality of movablehammers disposed on the opposite side of said web for striking said weband forcing it into contact with said ribbon and print roll combinationto produce a line of print, the improvement comprising tensioning meansdisposed after said feed mechanism for continuously applying a dynamictensile force of substantially constant value during the printingoperation to tension a web portion between said printing mechanism andsaid tensioning means.
 10. The structure as set forth in claim 9 whereinsaid tensioning means comprises a drive roll having an outer surfacewith a high coefficient of friction for contacting said web and whereinsaid drive roll rotation is effective to produce a tensile force in saidweb opposite to a tensile force produced in said web by contact of saidrotating print roll and ribbon combination with said web when struck byone of said hammers.
 11. The structure of claim 10 wherein saidtensioning means further comprises an idler roll with a surface having acoefficient of friction substantially less than that of said drive rollsurface, said idler roll being positioned to apply a force to said driveroll with said web disposed therebetween.
 12. The structure of claim 11which further includes means for adjustably increasing or decreasing themagnitude of force applied to said drive roll by said idler roll.
 13. Aprinter as set forth in claim 9 which further includes oTher tensioningmeans disposed along said path before said printing means for applying astatic drag force to said web in the opposite direction to said tensileforce.
 14. The method of feeding a paper web through a printer of thetype wherein a ribbon and rotating type roll are disposed adjacent oneside of the web and a plurality of movable hammers are disposed adjacentthe opposite side of the web to strike the web and force it into theribbon and rotating type roll to form a line of print on the web, whichincludes the steps of advancing the web in increments past the typeroll, printing upon said web by means of said plurality of movablehammers and said ribbon and type roll, and continuously applying asubstantially constant dynamic force on said web opposite the forceproduced on said web by contact of said type roll and ribbon combinationwith said web to maintain line registration of the web with said printroll during printing of an entire line.